/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License.  You may obtain a copy of the License at
    *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.omid.committable;
  
  import org.apache.phoenix.thirdparty.com.google.common.base.Optional;
  import org.apache.phoenix.thirdparty.com.google.common.util.concurrent.ListenableFuture;
  import org.apache.phoenix.thirdparty.com.google.common.util.concurrent.SettableFuture;
  import org.apache.omid.committable.CommitTable.CommitTimestamp.Location;
  
  import java.io.IOException;
  import java.util.concurrent.ConcurrentHashMap;
  
  public class InMemoryCommitTable implements CommitTable {
  
      final ConcurrentHashMap<Long, Long> table = new ConcurrentHashMap<>();
  
      long lowWatermark;
  
      @Override
      public CommitTable.Writer getWriter() {
          return new Writer();
      }
  
      @Override
      public CommitTable.Client getClient() {
          return new Client();
      }
  
      public class Writer implements CommitTable.Writer {
          @Override
          public void addCommittedTransaction(long startTimestamp, long commitTimestamp) {
              // In this implementation, we use only one location that represents
              // both the value and the invalidation. Therefore, putIfAbsent is
              // required to make sure the entry was not invalidated.
              table.putIfAbsent(startTimestamp, commitTimestamp);
          }
  
          @Override
          public void updateLowWatermark(long lowWatermark) throws IOException {
              InMemoryCommitTable.this.lowWatermark = lowWatermark;
          }
  
          @Override
          public void flush() throws IOException {
              // noop
          }
  
          @Override
          public void clearWriteBuffer() {
              table.clear();
          }
  
          @Override
          public boolean atomicAddCommittedTransaction(long startTimestamp, long commitTimestamp) throws IOException {
              startTimestamp = removeCheckpointBits(startTimestamp);
              // In this implementation, we use only one location that represents
              // both the value and the invalidation. Therefore, putIfAbsent is
              // required to make sure the entry was not invalidated.
              return (table.putIfAbsent(startTimestamp, commitTimestamp) == null);
          }
      }
  
      public class Client implements CommitTable.Client {
          @Override
          public ListenableFuture<Optional<CommitTimestamp>> getCommitTimestamp(long startTimestamp) {
              startTimestamp = removeCheckpointBits(startTimestamp);
              SettableFuture<Optional<CommitTimestamp>> f = SettableFuture.create();
              Long result = table.get(startTimestamp);
              if (result == null) {
                  f.set(Optional.<CommitTimestamp>absent());
              } else {
                  if (result == INVALID_TRANSACTION_MARKER) {
                      f.set(Optional.of(new CommitTimestamp(Location.COMMIT_TABLE, INVALID_TRANSACTION_MARKER, false)));
                  } else {
                      f.set(Optional.of(new CommitTimestamp(Location.COMMIT_TABLE, result, true)));
                  }
              }
              return f;
          }
  
          @Override
          public ListenableFuture<Long> readLowWatermark() {
              SettableFuture<Long> f = SettableFuture.create();
              f.set(lowWatermark);
             return f;
         }
 
         @Override
         public ListenableFuture<Void> deleteCommitEntry(long startTimestamp) {
             startTimestamp = removeCheckpointBits(startTimestamp);
             SettableFuture<Void> f = SettableFuture.create();
             table.remove(startTimestamp);
             f.set(null);
             return f;
         }
 
         @Override
         public ListenableFuture<Boolean> tryInvalidateTransaction(long startTimestamp) {
             startTimestamp = removeCheckpointBits(startTimestamp);
             SettableFuture<Boolean> f = SettableFuture.create();
             Long old = table.get(startTimestamp);
 
             // If the transaction represented by startTimestamp is not in the map
             if (old == null) {
                 // Try to invalidate the transaction
                 old = table.putIfAbsent(startTimestamp, INVALID_TRANSACTION_MARKER);
                 // If we were able to invalidate or someone else invalidate before us
                 if (old == null || old == INVALID_TRANSACTION_MARKER) {
                     f.set(true);
                     return f;
                 }
             } else {
                 // Check if the value we read marked the transaction as invalid
                 if (old == INVALID_TRANSACTION_MARKER) {
                     f.set(true);
                     return f;
                 }
             }
 
             // At this point the transaction was already in the map at the beginning
             // of the method or was added right before we tried to invalidate.
             f.set(false);
             return f;
         }
     }
 
     public int countElements() {
         return table.size();
     }
 
     static long removeCheckpointBits(long startTimestamp) {
         return startTimestamp - (startTimestamp % CommitTable.MAX_CHECKPOINTS_PER_TXN);
     }
 }